In a conventional blower, it is known to control balance of a fan so as to cancel vibrations between the fan and a motor as rotational members. The balance is controlled by adding a balance weight to the fan or reducing an excess weight from the fan. Controlling the balance by adding the balance weight is, for example, referred to as a plus balance control, and controlling the balance by reducing the excess weight is, for example, referred to as a minus balance control.
In general, the minus balance control is put into practice at a relatively low cost because the balance weight needs not to be added. As an example of the minus balance control, if a cutout portion is formed on a fan blade, which serves to force air out, air flow will be disturbed by the cutout portion. As a result, air blowing efficiency will be reduced and noise will be increased.